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Barrer
Barrer is a non- SI unit of gas permeability (specifically, gas permeability) used in the membrane technology and contact lens industry. It is named after Richard Barrer. Definition \rm \ barrer = \frac Here the 'cm3STP' is standard cubic centimeter, which is a unit of amount of gas rather than a unit of volume. It represents the number of gas molecules or moles that ''would'' occupy one cubic centimeter at standard temperature and pressure, as calculated via the ideal gas law. The cm corresponds in the permeability equations to the thickness of the material whose permeability is being evaluated, the cm3STPcm−2s−1 to the flux of gas through the material, and the cmHg to the pressure drop across the material. That is, it measures the rate of fluid flow passing through an area of material with a thickness driven by a given pressure. See Darcy's Law. In SI unit Barrer can be expressed as: \rm \ barrer = \frac To convert to CGS permeability unit, one must use the foll ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richard Barrer
Richard Maling Barrer FRS (16 June 1910 – 12 September 1996) was a New Zealand-born chemist. His areas of research included gas permeability of membranes and zeolite science, of which he was a founding figure; he also gave his name to the zeolite Barrerite. The Barrer, a unit of gas permeability, is also named after him. The son of New Zealand sheep farmers, his undergraduate degree was from Canterbury College (now University of Canterbury), in Christchurch, New Zealand. He followed this with a master's degree titled ''Studies in catalytic hydrogenation: the system HCN + 2H2=CH3NH2'', completed in 1931. In 1932 he received an 1851 Exhibition Scholarship which allowed him to study at Eric Rideal's Colloid Science Laboratory in Cambridge University. At Cambridge he was also a keen cross-country runner, winning the 1934 Oxford-Cambridge race and being awarded a Full Blue for Athletics. He received his PhD from Cambridge in 1935 and DSc's in 1937 (New Zealand) and 1938 (Cambridge) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semipermeable Membrane
Semipermeable membrane is a type of biological or synthetic, polymeric membrane that will allow certain molecules or ions to pass through it by osmosis. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. How the membrane is constructed to be selective in its permeability will determine the rate and the permeability. Many natural and synthetic materials which are rather thick are also semipermeable. One example of this is the thin film on the inside of the egg. Biological membranes are selectively permeable, with the passage of molecules controlled by facilitated diffusion, passive transport or active transport regulated by proteins embedded in the membrane. Biological membranes An example of a biological semi-permeable membrane is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Lens
Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic or therapeutic reasons. In 2010, the worldwide market for contact lenses was estimated at $6.1 billion, while the US soft lens market was estimated at $2.1 billion.Nichols, Jason J., et a"ANNUAL REPORT: Contact Lenses 2010" January 2011. Multiple analysts estimated that the global market for contact lenses would reach $11.7 billion by 2015. , the average age of contact lens wearers globally was 31 years old, and two-thirds of wearers were female.Morgan, Philip B., et al"International Contact Lens Prescribing in 2010" ''Contact Lens Spectrum''. October 2011. People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are main motivating factors for people who want to avoid wearing glasses or to change the appearance or c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Cubic Foot
A standard cubic foot (scf) is a unit used both in the natural gas industry to represent an amount of natural gas and in other industries where other gases are used. It is the unit commonly used when following the customary system, a collection of standards set by the National Institute of Standards and Technology. Another unit used for the same purpose is the standard cubic metre (Sm3), customary when using SI units. Definitions A standard cubic foot defines an amount of gas contained in a volume of one cubic foot at standard temperature and pressure. This standard unit of molecular quantity for gases can be used with the ideal gas law to compute the quantity per unit of volume for other pressures and temperatures. In spite of the label "standard", there is a variety of definitions, mainly depending on the type of gas. Since, for a given volume, the quantity is proportional to the pressure and temperature, each definition fixes base values for pressure and temperature. Natural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amount Of Substance
In chemistry, the amount of substance ''n'' in a given sample of matter is defined as the quantity or number of discrete atomic-scale particles in it divided by the Avogadro constant ''N''A. The particles or entities may be molecules, atoms, ions, electrons, or other, depending on the context, and should be specified (e.g. amount of sodium chloride ''n''NaCl). The value of the Avogadro constant ''N''A has been defined as . The mole (symbol: mol) is a unit of amount of substance in the International System of Units, defined (since 2019) by fixing the Avogadro constant at the given value.Bureau International des Poids et Mesures (2019): The International System of Units (SI)', 9th edition, English version, p. 134. Available at thBIPM website Sometimes, the amount of substance is referred to as the chemical amount. Role of amount of substance and its unit mole in chemistry Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope. As a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The definition of length (cubed) is interrelated with volume. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. In ancient times, volume is measured using similar-shaped natural containers and later on, standardized containers. Some simple three-dimensional shapes can have its volume easily calculated using arithmetic formulas. Volumes of more complicated shapes can be calculated with integral calculus if a formula exists for the shape's boundary. Zero-, one- and two-dimensional objects have no volume; in fourth and higher dimensions, an analogous concept to the normal vo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Conditions For Temperature And Pressure
Standard temperature and pressure (STP) are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. In chemistry, IUPAC changed its definition of standard temperature and pressure in 1982: * Until 1982, STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 atm (101.325 kPa). * Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 105 Pa (100 kPa, 1 bar). STP should not be confused with the standard state com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ideal Gas Law
The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stated by Benoît Paul Émile Clapeyron in 1834 as a combination of the empirical Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. The ideal gas law is often written in an empirical form: pV = nRT where p, V and T are the pressure, volume and temperature; n is the amount of substance; and R is the ideal gas constant. It can also be derived from the microscopic kinetic theory, as was achieved (apparently independently) by August Krönig in 1856 and Rudolf Clausius in 1857. Equation The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation relates these simply in two main forms. The temperature used in the equation of state is an absolute temperature: the appropria ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centimeter
330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter. A centimetre (international spelling) or centimeter (American spelling) (SI symbol cm) is a Units of measurement, unit of length in the International System of Units (SI), equal to one hundredth of a metre, ''centi'' being the SI prefix for a factor of . The centimetre was the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units. Though for many physical quantities, SI prefixes for factors of 103—like ''milli-'' and ''kilo-''—are often preferred by technicians, the centimetre remains a practical unit of length for many everyday measurements. A centimetre is approximately the width of the fingernail of an average adult person. Equivalence to other units of length : One millilitre is defined as one cubic centimetre, under the SI system of units. Other uses In ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In vector calculus flux is a scalar quantity, defined as the surface integral of the perpendicular component of a vector field over a surface. Terminology The word ''flux'' comes from Latin: ''fluxus'' means "flow", and ''fluere'' is "to flow". As ''fluxion'', this term was introduced into differential calculus by Isaac Newton. The concept of heat flux was a key contribution of Joseph Fourier, in the analysis of heat transfer phenomena. His seminal treatise ''Théorie analytique de la chaleur'' (''The Analytical Theory of Heat''), defines ''fluxion'' as a central quantity and proceeds to derive the now well-known express ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Darcy's Law
Darcy's law is an equation that describes the flow of a fluid through a porous medium. The law was formulated by Henry Darcy based on results of experiments on the flow of water through beds of sand, forming the basis of hydrogeology, a branch of earth sciences. It is analogous to Ohm's law in electrostatics, linearly relating the volume flow rate of the fluid to the hydraulic head difference (which is often just proportional to the pressure difference) via the hydraulic conductivity. Background Darcy's law was first determined experimentally by Darcy, but has since been derived from the Navier–Stokes equations via homogenization methods. It is analogous to Fourier's law in the field of heat conduction, Ohm's law in the field of electrical networks, and Fick's law in diffusion theory. One application of Darcy's law is in the analysis of water flow through an aquifer; Darcy's law along with the equation of conservation of mass simplifies to the groundwater flow equation, one of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permeance
Permeance, in general, is the degree to which a material admits a flow of matter or energy. Permeance is usually represented by a curly capital P: \mathcal. Electromagnetism In electromagnetism, permeance is the inverse of reluctance. In a magnetic circuit, permeance is a measure of the quantity of magnetic flux for a number of current-turns. A magnetic circuit almost acts as though the flux is conducted, therefore permeance is larger for large cross-sections of a material and smaller for smaller cross section lengths. This concept is analogous to electrical conductance in the electric circuit. Magnetic permeance \mathcal is defined as the reciprocal of magnetic reluctance \mathcal (in analogy with the reciprocity between electric conductance and resistance): : \mathcal = \frac which can also be re-written: : \mathcal = \frac using Hopkinson's law (magnetic circuit analogue of Ohm's law for electric circuits) and the definition of magnetomotive force (magnetic analogue of elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
